The present invention relates generally to the field of separation technology. More particularly, it concerns a continuous chemical separation process wherein a solute is removed from a fluid process stream by attachment to a sorbent at a liquid-solid interface.
Chemical separation processes that utilize solid sorbents to remove solutes from fluids at liquid-solid interfaces employ various methods to contact the fluid process stream with the solid sorbents including continuous methods wherein a moving sorbent bed contacts the process stream and periodic methods wherein fixed beds are contacted with the process stream. Often two fixed bed adsorbers are provided with periodic methods so that one is on stream while the other is being regenerated. If the loading rate of the solute on the sorbent is high, multiple fixed beds may be necessary in order to maintain one in service, and in this case a single continuous unit may be designed to provide the same capacity with reduced capital and space requirements. Continuous processes typically use moving beds of sorbent that are transported in the form of loose granules or pellets, either hydraulically or with mechanical conveyers through the process system apparatus. Though characterized as continuous processes, systems that utilize moving sorbent beds typically interrupt the process fluid flow while the bed is moved. The overall benefits of a continuous process system can be diminished by problems associated with mechanical complexity of equipment, gradual attrition of solid sorbent, limitations in particle size to avoid classification or excessive pressure drop, and channeling of either the process stream or solid sorbent.
Regeneration methods to remove adsorbed solute from the sorbent include pressure swings and temperature swings. Pressure swing techniques are generally limited to closed systems that can be pressurized. Temperature swing techniques are generally limited to the rate of heat transfer for both elevating the temperature and subsequently lowering it.
Accordingly, the present invention provides a process for removing a solute from a fluid process stream comprising (a) continuously contacting the process stream with a portion of a rotating mass of sorbent material at a temperature that allows sorption of the solute by the Ad sorbent material to form a solute-adsorbed portion of sorbent material; (b) continuously rotating the mass of sorbent material; (c) raising the temperature of the solute-adsorbed and rotated portion of sorbent material by contacting said portion with an eluant stream having a temperature that allows release of the solute to form an eluted portion of sorbent material; and (d) cooling the further rotated and eluted portion with a cooling stream to form regenerated portion of sorbent material; simultaneously with steps a-d collecting product stream containing solvent, and continuously repeating the above-named steps.
The basics of the present invention include adsorbing on a sorbent material a solute from a first fluid stream at a first temperature, desorbing the solute with a second fluid stream at a second temperature which is greater than the first temperature, and regenerating the sorbent material with a third fluid stream at a temperature less then the second temperature. These steps are accomplished by continuously moving the sorbent material and without interruption of the fluid streams.
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